<style>
    div,
    span {
        border: 1px solid lightgray;
        margin: 10px;
        width: 200px;
        height: 100px;
    }
    
    .d {
        display: block;
    }
</style>

<div>普通的div块</div>
<span>这是普通span</span> <span>这是普通span</span> <span>这是普通span</span>
<span class="d">这是span,被改造成了块级元素</span>